They are asking people who are in lockdown what their "sentiments." It's like asking a person who just finishes a crappy 18 hour shift. Guess how many of them will say they'll quit vs who actually quit.
They are asking business owners
Its like asking a normal businessman on what to do about his business, seems pretty normal to me.
Guess how many of them will increase or decrease investment.
In any case, its pretty normal to make surveys even when they are on lockdown. Its a survey, that's what they supposed to do, to get responses and then release the results. Now if they are going to change their minds later on (I assume that's your argument) is irrelevant because they can simply take another survey next month/weeks and then release more results.
90% is a huge number though. Of course, this is an exaggerated response by the business owners but it still provides a valuable metric to grasp Shanghai's SMEs in the service industry.
Given the recently released Caixin PMI services number, I would trust the survey results more if I were you (not saying that they are 100% correct though)